Primary Components of a Breeding Program
1- Develop a Vision or a Breeding Goal
Every breeding program should begin by developing a breeding goal. Why are you trying to make seed? What are you trying to accomplish by mating these sets of parents? You might be trying to make a seed population that represents the traits of an ideal, or mostly ideal plant you have previously selected. In the case of the latter, you might be trying to add new traits to your mostly ideal plant and incorporate these new traits into a new seed line. Some may just want some seeds to plant for next year’s crop. Think of your breeding goal as your final destination; the breeding process is the roadmap or route to get to that goal.
2- Find or Create Variability
Finding variable seed lots these days is certainly not a difficult task, because very few breeders take the time to stabilize or fix certain traits within a given breeding population prior to release. Your starting seed stock likely represents a range of variation for most traits, depending on the source of your initial starting material. The sad reality is that most of the seed industry today focuses more on creating seed for sale than on developing improved or even uniform plant stock. As a breeder looking for germ plasm to work with, this leaves unstable populations with ample variation for future selection. If searching for variation, this could be considered a good thing. However, since true-breeding stable plants are what breeders look for when choosing stock for their own breeding, this is a hindrance as well. It is much easier to breed with true breeding plants because one can see patterns emerging in a predictable manner in subsequent generations, and thus expect reliable, consistent results when hybridizing known true-breeding parents. This can only be achieved if the breeder is using true-breeding starting parent stock. Due to the lack of commercially available true-breeding stock to work with, serious breeders must stabilize their initial breeding stock before beginning the hybridizing or outcrossing phases of their breeding programs.
3- Grow and Evaluate
The more plants you grow, the more variations you will see. Cannabis is an extremely variable and polymorphic species, many traits have numerous possible expressions. Growing varied seed stocks of different heritage ( and many of each population) ensures the breeders a wide array of phenotypes and combinations of traits for future selection.
Choosing from as many plants as possible is always preferable; having a wide and diverse starting stock assures the highest chances of finding what you might be looking for. When selecting from just a few seeds, it’s not possible to assure all plants will be vigorous or show the traits of interest even if they are seeds of known quality. Breeders must weed through large populations of potential plants, and “rogue out” the undesirable individuals. In any breeding program, off-types which do not suit the goal should be removed from the breeding populations.
Some recessive traits, especially those controlled by multiple genes (polygenic traits), have the potential for phenotypes that are only apparent in 1 in 100 or even 1 in 1000 plants. Unless growing many individuals, the breeder has a very low likelihood of discovering these phenotypes. All other things being equal, the breeder who grows the most plants has the greatest possibility of finding the best breeding candidates. Testing the final product is a crucial part of the evaluation process.
4- Screen, Select, and Apply Selection Pressures
Breeders select plants for future breeding on the basis of their desirable characteristics. There is no “right” or “correct” ranking of priority for selecting one trait over another; this is purely based on what traits are most important to the breeder. For indoor cultivation, these include short, squat, bushy growth; large, densely formed buds; discernible taste or particular flavors and aromas; high THC content and quality of high; and resistance to specific insects or diseases. It’s a good general rule to look for plants with overall vigor and good health.
Sometimes, we find a plant that is almost ideal in every respect, but has some negative trait that in undesirable. For example, the breeder may select a highly potent plant that produces exceptionally aromatic or flavorful flowers but is tall and lanky and difficult to grow indoors under artificial light. Even with this negative trait, the breeder decides the plant is a worthwhile breeding candidate. The breeder must realize and note that when selecting plants that may have some genetic weakness, the unwanted negative traits must be removed from the population at a later point. The breeder must balance positive and negative aspects of each plant as a possible genetic contributor to future generations.
When planting a large number of seeds, you will generally find that some plants differ greatly in regard to certain traits while being otherwise nearly identical. For example, some plants are more-or-less susceptible to fungal infection such as botrytis (grey mold) or powdery mildew. Once suitable plants are selected, they can be exposed to a particular pathogen or environment as a selection pressure; growing potential breeding parents in an environment may expose genetic strengths or weaknesses associated with a particular environment. For mold resistance varieties, select plants for future mating that resist mold in a mold prone environment. For potent varieties, select only the most potent plants, after harvest. If you require your plants finish at less than 6 feet of height, remove or only keep seeds from plants that mature at less than 6 feet. If you require an outdoor acclimated variety, perform your selection outdoors under those particular conditions, and pit an emphasis for selection on plants that mature early enough to finish in your particular environment. Selecting the earliest of the most potent plants is a better way to preserve potency, than selecting the most potent of the early plants. It really depends on what traits the breeder ranks in importance to the program, a decision based on the breeding goal.
Usually, varieties that perform well under artificial lights will also perform well outside or in a greenhouse under natural sunlight after two or three years of acclimation. The converse doesn’t hold true nearly as often. Varieties that perform well outside, especially pure sativa varieties, often prove disappointing when grown under artificial light.
Post-harvest selection requires either partial seeding of each plant (only seeds from the most potent plants are sown for successive generations) or keeping clone copies of each and every plant, for future seed production use once post harvest evaluations are done.
